We discuss the cosmological implications of the new constraints on the power spectrum of the Cosmic Microwave Background Anisotropy derived from a new high resolution analysis of the MAXIMA-1 measurement (Lee et al. 2001). The power spectrum shows excess power at $\ell \sim 860$ over the average level of power at $411 \le\ell \le 785.$ This excess is statistically significant on the 95% confidence level. Such a feature is consistent with the presence of a third acoustic peak, which is a generic prediction of inflation-based models. The height and the position of the excess power match the predictions of a family of inflationary models with cosmological parameters that are fixed to fit the CMB data previously provided by BOOMERANG-LDB and MAXIMA-1 experiments (e.g., Jaffe et al.2001). Our results, therefore, lend support for inflationary models and more generally for the dominance of coherent perturbations in the structure formation of the Universe. At the same time, they seem to disfavor a large variety of the non-standard (but still inflation-based) models that have been proposed to improve the quality of fits to the CMB data and consistency with other cosmological observables. Within standard inflationary models, our results combined with the COBE-DMR data give best fit values and 95% confidence limits for the baryon density, $\Omega_b h^2\simeq 0.033{\pm 0.013}$, and the total density, $\Omega=0.9{+0.18\atop -0.16}$. The primordial spectrum slope ($n_s$) and the optical depth to the last scattering surface ($\tau_c$) are found to be degenerate and to obey the relation $n_s \simeq 0.46 \tau_c + (0.99 \pm 0.14)$, for $\tau_c \le 0.5$ (all 95% c.l.).

With detections of the Sunyaev-Zel'dovich (SZ) effect induced by galaxy clusters becoming routine, it is crucial to establish accurate theoretical predictions. We use a hydrodynamical N-body code to generate simulated maps, of size 1 deg², of the thermal SZ effect. This is done for three different cosmologies: the currently favoured low-density model with a cosmological constant, a critical-density model and a low-density open model. We stack simulation boxes corresponding to different redshifts in order to include contributions to the Compton y-parameter out to the highest necessary redshifts. Our main results are as follows.

We use a combination of the most recent cosmic microwave background (CMB) flat-band power measurements to place constraints on Hubble's constant h and the total density of the universe Ω₀ in the context of inflation-based cold dark matter (CDM) models with no cosmological constant. We use χ² minimization to explore the four-dimensional parameter space having as free parameters, h, Ω₀, the power-spectrum slope n, and the power-spectrum normalization at ℓ = 10. Conditioning on Ω₀ = 1, we obtain h = 0.33 ± 0.08. Allowing Ω₀ to be a free parameter reduces the ability of the CMB data to constrain h, and we obtain 0.26 < h < 0.97 with a best-fit value at h = 0.40. We obtain Ω₀ = 0.85 and set a lower limit Ω₀ > 0.53. A strong correlation between acceptable h and Ω₀ values leads to a new constraint Ω₀h^1/2 = 0.55 ± 0.10. We quote Δχ² = 1 contours as error bars; however, because of nonlinearities of the models, these may be only crude approximations to 1 σ confidence limits. A favored open model with Ω₀ = 0.3 and h = 0.70 is more than ~4 σ from the CMB data best-fit model and is rejected by goodness-of-fit statistics at the 99% confidence level. High baryonic models (Ω_bh² ~ 0.026) yield the best CMB χ² fits and are more consistent with other cosmological constraints. The best-fit model has n = 0.91^{+ 0.29}_−0.09 and Q₁₀ = 18.0^{+ 1.2}_−1.5 μK. Conditioning on n = 1, we obtain h = 0.55^{+ 0.13}_−0.19, Ω₀ = 0.70 with a lower limit Ω₀ > 0.58, and Q₁₀ = 18.0^{+ 1.4}_−1.5 μK. The amplitude and position of the dominant peak in the best-fit power spectrum are A_peak = 76^{+ 3}₋₇ μK and ℓ_peak = 260^{+ 30}₋₂₀. Unlike the Ω₀ = 1 case we considered previously, CMB h results are now consistent with the higher values favored by local measurements of h but only if 0.55 Ω₀ 0.85. Using an approximate joint likelihood to combine our CMB constraint on Ω₀h^1/2 with other cosmological constraints, we obtain h = 0.58 ± 0.11 and Ω₀ = 0.65^{+ 0.16}_−0.15.

The Square Kilometre Array (SKA) will be the world’s largest and most sensitive radio telescope. It will address fundamental unanswered questions about our Universe including how the first stars and galaxies formed after the Big Bang, how dark energy is accelerating the expansion of theUniverse, the role of magnetism in the cosmos, the nature of gravity, and the search for life beyond Earth. This project envisages the construction of 133 15-m antennas in South Africa and 131072 log-periodic antennas in Australia, together with the associated infrastructure in the two desert sites. In addition, the SKA is an exemplar Big Data project, with data rates of over 10 Tbps being transported from the telescope to HPC/HTC facilities.

We use hydrodynamical simulations to assess the impact of radiative cooling and `pre-heating' on predictions for the Sunyaev--Zel'dovich (SZ) effect. Cooling significantly reduces both the mean SZ signal and its angular power spectrum, while pre-heating can give a higher mean distortion while leaving the angular power spectrum below that found in a simulation without heating or cooling. We study the relative contribution from high and low density gas, and find that in the cooling model about 60 per cent of the mean thermal distortion arises from low overdensity gas. We find that haloes dominate the thermal SZ power spectrum in all models, while in the cooling simulation the kinetic SZ power spectrum originates predominantly in lower overdensity gas.Comment: 4 pages LaTeX file with five figures incorporated. Various clarifications to the discussion. Further colour images and animations at http://astronomy.susx.ac.uk/users/antonio/sz.htm